Fluorescence-activated cell sorting is a technology that allows rapid separation of single cells based on thier size and fluorescence proprties. This technology has been applied extensively in the area of immunology research and has permitted a number of advances not previously possible. The potential of this technology is very great because of the wide variety of fluorescent probes that can be used to study the cell. FACS technology is now beginning to have an effect on other fields of biomedical research and on clinical medicine. This proposal is to place a state-of-the-art research-grade FACS into a hospital environment for use in a variety of projects that range from basic research to clinical applications. Potential uses for such a device in our hospital include the study of: 1) human lymphoma and leukemia; 2) the developmental sequence of human monocytes and macrophages; 3) the function of renal endocrine cells; 4) the function of subsets of adrenal cells; 5) the immunobiology of the B lymphocyte; 6) viral receptors on cells of the nervous sytem; 7) T cell subsets in patients with multiple sclerosis; 8) T cell-macrophage interactions; 9) platelet structure and function; 10) anti-platelet antibodies; 11) immunosuppression after severe trauma; and 12) the formation of new monoclonal antibodies for biomedical research. The FACS will become a central feature of the research efforts of many investigators at the hospital and will greatly expand our ability to make progress in each of these diverse areas.